Biomass, such as livestock manure and excess sewage sludge is generally known as a material comprising organic resources originating from living organisms. Excess sewage sludge is the sludge obtained after biological treatment of nitrogen-containing organic waste that is discharged as sewage from homes for instance. Biomass is drawing attention because, unlike fossil resources like petroleum, it is reusable, as resources, such as compost or energy, without increasing the atmospheric carbon dioxide. However, in most cases, waste originating from living organisms cannot be used as is as biomass, and needs to be given specific treatments. For example, nitrogen-containing wastes like livestock manure and excess sewage sludge cannot be discarded as such or reused as compost for instance. The nitrogen-containing waste needs treatment for removal of malodorous components like ammonia, for reduction of its water content. For example, in methods of microbial decomposition and fermentation treatment of organic wastes, in which the waste is simply left as such, malodorous components such as fatty acids and amines are produced further. Therefore, treatment to reduce the bad odor of the organic waste is essential. In decomposition and fermentation methods, which allow the natural course of events to occur, such as leaving the waste under conditions where multiple types of microbes coexist, have problems such as instability and non-reproducibility of the decomposition treatment.
Conventionally, organic materials such as sawdust are mixed with livestock manure for reducing the water content, such as from urine, in the manure, as a method of absorbing and dispersing the moisture in the manure into the organic material. The carbon component of the livestock manure is present only in the form of dietary fibers, which are digestion residues of the livestock, and the aforesaid organic material, and very little of the carbon component in the livestock manure is in forms usable by microorganisms. Nitrogen components like proteins are in excess in the livestock manure, which results in the production and accumulation of ammonia, making the pH of the manure alkaline. The release of a proton from the ammonium ion in the livestock manure gives rise to ammonia gas, which is then dispersed into the atmosphere as a malodorous substance. These are the major problems in the early methods of composting.
The method of adding a microbial material and a carbon component such as a sugar or an organic acid to the material to be treated, as described in Patent Documents 1 to 3, is known as means of solving the aforementioned problems. Known commercially available carbon components of the aforesaid type include Fieldcompo, Cattlecompo, Caloriecompo, Accelcompo, and Assistcompo from Nisshin Flour Milling Inc. At the actual site of the composting treatment, wood vinegar is added, a carbon component is added for accelerating the fermentation, and a commercially available deodorant is used.
However, the decomposition reaction of the material to be treated by the aforesaid microbial material is an oxidative decomposition reaction. Therefore, when substances that can be easily assimilated by the microorganism, such as organic acids and sugars, are present in the material to be treated, the oxygen in the material to be treated is rapidly consumed through respiration by the microorganism. As a result, the inside of material to be treated becomes oxygen-poor (anaerobic), and organic acid accumulates in the process of sugar metabolism, and this lowers the pH of the material to be treated. Thus, although it is possible to prevent the emanation of ammonia odor from the material to be treated, methane gas, a known greenhouse gas, is produced, and odors other than of ammonia arising from the dispersal of low molecular weight organic acids are produced. Also, a long time is needed for the complete curing of the material to be treated because of the anaerobic fermentation. Moreover, attempts made to lower the water content of the material to be treated only by blending organic materials increase the bulk of the material to be treated, and this increases the time required to compost it.
There have also been attempts to solve the aforesaid problems by adding not only carbohydrates, but also oils produced as food waste, for instance, to the material to be treated. But there are some concerns about this method, including the lack of oxygen arising from poor aeration when the compost becomes more fluid, and the damage to germination of crop plants from the undecomposed oils in the compost thus prepared.
The methods of treating with the specific microorganisms described in Patent Documents 4 to 6 are known as biological methods of treating the malodorous gases like ammonia and amines produced during the fermentation of organic wastes. Patent Document 4 discloses a method of blending Bacillus badius with livestock feces to reduce malodorous substances such as ammonia through assimilation. Patent Document 5 discloses a method of reducing odor and water content of the organic raw material by blending hyperthermophilic bacteria of the genera Bacillus, Micrococcus, etc with organic raw materials like livestock feces and sewage sludge, and fermenting the organic raw material while aerating it. Patent Document 6 discloses a method of preventing the generation of odor by assimilation of malodorous compounds such as ammonia by using microorganisms like Bacillus smithii. Apart from the aforesaid methods of preventing the generation of odor by the assimilation of ammonia, etc, the method of preventing odor generation by nitrification and denitrification using microorganisms is also known. In this method, ammonium ions, nitrite ions, and nitrate ions are removed as nitrogen by the actions of nitrifying bacteria (ammonia oxidizing bacteria and nitrite oxidizing bacteria) and denitrifying bacteria.
Patent Document 1: U.S. Pat. No. 5,364,788
Patent Document 2: Japanese Patent No. 2553727
Patent Document 3: Japanese Laid-Open Patent Publication No. 2000-197478
Patent Document 4: Japanese Laid-Open Patent Publication No. 07-163336
Patent Document 5: Japanese Laid-Open Patent Publication No. 11-292674
Patent Document 6: Japanese Laid-Open Patent Publication No. 2005-130820